The present invention relates to a rubber stopper for a waterproof connector and more particularly to improvements in rubber stoppers for waterproof connectors, which rubber stopper is inserted into the terminal receiving hole of a connection-terminal holding chamber of a connector housing in order to hermetically seal the connection-terminal holding chamber in a liquid-tight fashion.
Heretofore, a typical conventional waterproof connector intended to prevent the penetration of water and the like from the outside has been so designed that a rubber stopper is provided for the electric wire of each connecting terminal inserted into the connection-terminal holding chamber (hereinafter also called "cavity") of a connector housing.
When a multi-polar connector is used, however, the presence of an unused connecting terminal allows water to penetrate into a free cavity through its terminal receiving hole. Consequently, a waterproofing rubber stopper 3 is inserted into the terminal receiving hole of a free cavity 2 as shown in FIG. 1, whereby the free cavity 2 is hermetically sealed in a liquid-tight fashion to prevent moisture from penetrating into a connector housing 1.
The conventional waterproofing rubber stopper 3 used in the waterproof connector like this has generally been formed by molding a soft rubber material into a columnar-shape. However, there is the possibility that the waterproofing rubber stopper 3 falls out of the connector housing 1 when the internal pressure rises at the time of fitting the connecter in, for example, because the waterproofing rubber stopper 3 is normally formed soft so as to increase the adhesive properties of the inside wall surface of the terminal receiving hole of the free cavity 2.
As disclosed in Japanese Utility Model Unexamined Publication No. Hei. 2-7874, a blank plug (waterproofing rubber stopper) for a waterproof connector is consequently formed by covering the periphery of a core material molded from a hard material with a soft sealing material having a wavy surface in cross section in order to secure waterproofness and to make the blank plug hardly come off a terminal receiving hole.
Even in the case where the blank plug is used for a waterproof connector as disclosed in the Japanese Utility Model Unexamined Publication No. Hei. 2-7874, the adhesive properties of the inside wall surface of the terminal receiving hole of the free cavity 2 are insufficient and when the internal pressure rises at the time of fitting the connector in, there is still the possibility that the blank plug displaces backward in the free cavity 2, thus ruining sealing performance or causing the blank plug to slip off the free cavity 2.